1. Field of the Invention
The present invention relates to an apparatus and method for forming a pipe seat frame for use in a seat for a vehicle such as an automobile, and, more particularly, to such apparatus and method for bending a rectilinear pipe material to form a pipe frame of a predetermined configuration.
2. Description of the Prior Art
As a seat frame for a vehicle seat a pipe frame formed of a pipe material is employed in view of reduction of the weight of such seat, and such pipe frame is provided in its side portions with spring clamps welded thereto so as to extend spring members for carrying a seat pad.
Conventionally, a pipe frame of this type is formed by bending a pipe material into an endless configuration and thereafter welding spring clamps to such endless pipe material in position. However, since such a pipe frame must have a bent form in its longitudinal direction or in its forward and rearward direction as well, when it is desired to automate such pipe frame forming process, it is found difficult to automate operations for supplying such pipe frames, setting the spring clamps in their predetermined positions of the associated pipe frame, and so on.
In a typical prior art process for forming a pipe frame, therefore, a general purpose bending apparatus is used to bend a pipe material and both ends of the bent pipe material are then butt welded together at their faces, or welded together via a core steel material to provide an endless configuration before spring clamps are welded to such endless pipe frame using a special welding apparatus.
In this prior art forming process, however, the number of man-hour in transporting such pipe materials between the work stations involved therein is quite large and thus a poor efficiency of operation results.
In addition, with such conventional forming technique, as mentioned above, the ends of such pipe materials are welded together in one of two ways. In one of them, the ends are butt welded to each other with their faces engaged together. In the other way, a core steel material is inserted into a pipe material in a manner to extend along both of the inside diameter portions of the pipe ends and thereater it is welded to such two ends respectively. Consequently, in the former case, spatters that are scattered around during welding may penetrate into the interior of the pipe material and remain contained therein. Because such spatters will produce noises while they are moved within the pipe frame, products containing such spatters therein are considered as defective and rejected, providing a poor yielding rate.
In the latter case, since both of the ends of the pipe material must be welded relative to the core steel material, the welding operation requires more time and labor. Also, such welding operation by means of the core steel material results in the increased weight of the pipe frame itself, which provides an unfavorable condition for a vehicle seat the entire weight of which is desired to lighten.